The present invention relates generally to side impact gas inflators for automotive passenger restraint systems, and more specifically, to a gas generator therein for improved cooling of combustion gases.
Certain features of a conventional forward-mounted airbag prevent its corresponding use as a side impact airbag. The size of the inflator constitutes one primary difference. The speed of deployment is yet another difference; to meet design specifications, side impact airbags must deploy significantly faster than forward-mounted airbags. Generally speaking, side impact inflators that are stored within the seat are desirable. One drawback, however, is that the size of the inflator may significantly detract from the comfort of the seat. Because of this, many known forward-mounted inflator systems are simply to large and to slow to function as a seat-mounted side impact airbag. It is therefore desirable that the side impact inflator be substantially smaller and deploy significantly faster than its forward-mounted counterpart.
The size limitation may pose several disadvantages with regard to inflator operability. For example, heat, as well as particulates, in the combustion of gases produced by a pyrotechnic inflator of a vehicle occupant restraint system, must be attenuated prior to discharge thereof into the passenger compartment of the vehicle. While the industry has been successful in meeting current standards through the use of azide propellants, the advent of a new class of nonazide propellants has complicated the problem due to high combustion temperatures and due to the characteristics of particulate combustion. A reduction in inflator size would likely correspond to a reduction in the size of the filter and heat sink within the gas generator. Because nonazide fuels, as compared to azide fuels, generally combust at greater temperatures, a more effective heat sink is required to shield the occupants from high heat exposure during airbag deployment. Additionally, the smaller inflator must be equipped with a filter that will effectively separate the solid and gaseous products of combustion. It is therefore further desirable that a smaller side airbag be equipped with a heat sink and filter every bit as effective as those within a conventional inflator.
Finally, the smaller airbag must deploy within 30 milliseconds or less to ensure occupant protection. Any longer deployment speed significantly detracts from the usefulness and protective capability of a side impact airbag. Therefore, although a smaller inflator will often correspond to a smaller amount of propellant, the gas generating capabilities must sufficiently pressurize the airbag and must also result in deployment speeds faster than those associated with larger inflators.
Thus, there is a requirement for a side impact airbag inflator that rapidly deploys and utilizes the many attributes of a non-azide propellant, and yet meets all current and projected standards for heat attenuation and particulate filtration from the gas produced.